Using mammalian cells cultured in vitro, a series of experiments will be performed at the NASA cyclotron in Cleveland, which is currently being used to treat patients with beams of fast neutrons. It is proposed to use a higher energy beam utilizing the proton on beryllium reaction. The purpose of the experiments is to characterize the beam by determining the relative biological effectiveness as a function of depth, and to provide information to help in the design of hydrogenous filters to harden the beam. Experiments with electron affinic compounds are designed to study the mechanism of their cytotoxic action. A number of newly synthesized compounds are available which will be compared with Misonidazole with regard to their radiosensitizing efficiency and their cytotoxicity. The interaction of a range of commonly used chemotherapy agents with naturally occurring polyamines is under study. Also the interaction of these agents with hyperthermia and with the electron affinic sensitizers.